Pressure system for submersible structures



Patented June 29, 1954 PRESSURESYSTEM FOB 'SUBMERS IBLE STRUCTURES--= IFrederiok-0,Luenbe1:ger, LosAngeles; CaliiZ, as-

signer to U; S.. Electrical Motors,- Inc, Los'Angelsflf CalifJ," "a"corp'oration-v of California Ap lication Decembelfi26, 1950 S'erialNoi-202, 719

6 Claims. (01. 103 -87) This? invention, relates $130 submersible:structures, such as a motor-pump unit adapted tooperate in a Well.

- In suchssubmersible'structures iitisaof fundamental importanceto-prevent-tentryot well fluidintoith'e motor casing; The. well fiuid inwhich:

theiii-nitzais designed to operateordinarilyoar-- ri'estsuspendedparticles of grit;v as: well: as other, foreignY-cmatten that is:likely: to harm-the. statorwinziings'andthearotatingaparts: of 1 the-motor.:

Butefonthe rotatingshaift that necessar-ily extends bey'ondrrthe motorcasing: for 1 cooperation Witt-r1thenpumpnitgis v a simple matter .toprovide sh aiuzanmthexmotor casing, It. hasbeenfound thatsea-ls-;mays:be efiective'ly' used,.provided= that there?existsliwithin'the" motor casing. aifiuid liamngeapressureiexceedingithatzofthe W elLfluicl om the';'. outside: ofrtheseal. The internal motor: fluid that is often-used-isinert -oi-1,. orthe like. The fnnct-iontof this:increasedrpressuretiscto insurezrthatthe" leakage thatmmay 7exist; however smail iis; outwardly zof the-ncasing :throug-hathe runnin-gtseal; .sthereby-qmainta-ining the-purityof thetmotor fluirtrwithin thecasingL-a i. Itzistan. object-of this:inventionsto: providean improved system-1for wmain-tainingaa substantialexcess'spressure of the internal motor fluidfwhereiby effective".ioperation zofthewseal is achieved :to. exoludeitherwellifluidt; V

It: is: anotheri. object; of thisrinventioneto:=pro video): compactsubmersibleunit. in'- which areser a-v voin oi:m'otoiifiluid;;ist=provid;ed:nss a =-part:-:of-v thesubmersibleltstructurei itself, together: with-:novelhaeangafbrsrelevatixig: thezpressureasofsi the motor fluid withinth'eireservoir: 1:1. o

Tlietexcessipressure ln'ecessamyiior. eifec'tiv'erzopi ei a-tion of thesealisdependent upomthe :rota -J some speed of the appartus; Iti isaccordingly; another object -ofi' this invention to provide systerrrtliatewi'll supplyan excess pressure in an amount idependent upon therotational speed ofi the apparatus.

7 It still-another object- 01i this ihye'ntl-on to uti1ize;="=---tl 'ie'veloeityorpressure: head deve l'oped i pump a submersib1e=-' motor-pumpun itto-supply'a'ii excess pre'ssure' to theimotor casing fluidi'rranamount dependent upon tlie rotational speed 'of the apparatusi I;

lt' is still aimtlier object of this "inventionilo utili'ze-thewapercliaraeteristfcs ofavolatilema emerges-causean-emesspressure inth'efintbr nal'motor casing fluid in order to securean-efliectivewopera'tion-of the sealing means to prevent ingress of Wellfluid into the motor casing.

This? invention-possesses many other advan I tages, andi'has otherobjects-Which'maybe made more clearly apparent froma considerationofseveral: embodiments of the invention; For this purpose there areshown aiew vforms'in the draw ings accompanying and forming-part of thepres-' These forms will now be described-in detail, illustrating-the:general" principles ofth'e invention; but itis to be understood that:thisxdetailed' description is not to be taker-1+ in a limiting sense,since the scope ofthe inven tion is: bestdefined'bythe appended claims;

Referring-to the drawings:

Figure 1 is a diagrammatio'view, mostly in section, illustrating amotor-pump unit in opere ativeposition in awellgand embodying one formof this invention;

Fig. 2 is'aview similar to Fig. 1, but illustrating a modified form ofthis'invention; and

Fig. 3 is an enlarged fragmentary sectional View illustrating, byway ofexample,-aseal that may! beused in thezstructure'. i

In the drawingsflhereis illustrated a submersi ole-unit in a Well casingit, the unit being dis-- posed below the level! I of the well fluid IZthere in. The unit comprises a pump I3, Whi'ch may be'of the centrifugaltype; and a motor 14. -'I-he"- motor i4 is coupled to the pump 13'structurally by a :irame l5, and rotatively by the couplingfkl 6 thatisconneeted to the pump shaft I? and" the motorlshaft Iii-respectively;

The motor stator-windings H! are enclosewby a casi'ng 26; together withupper and lowerend brackets 21: and 22 that are secured in'fluid tight,relation-to the casing zil'. These'bracketst'l and- 22 house suitablebearingstructures 23 and" 2.1 for'themotor shaft is irluid such asoilz'havin'g? insulating properties completely fill's -thei rnotor'casings i Asuthe shafti idextends through: tlie-umfa'ei' end-bracket- 2!it is'necessary there to p'rovi'd'e a sealing i, structure "to- 1prevent entry" of? Well fluidl?.. A sealingstruoture that' 'may beused'isiillustrated inFig. 3.

Theoseal comprises in essence, a stationary:

member mountedx on the: casing 2a and; a rotary member mounted on theshaft iii. A sleeve i together with ring 2 t accommodates the rubbingstationary elementatl' thatil'is providedwith a frustowonicalsurface;The stationary seaung: elements 25 2 6; and-2lare in'sertable intoatubular extension- 2 1 d-o'f the 1 upper end bracket "2i in fluid-tightrelation therewith. The element 21 may be of special wear-resistantmaterial. A rotating element 28 is carried by the shaft I8. Thisrotating element 23 has a surface mating with the frusto-conical surfaceof the stationary element 21, and in rubbing rotational contacttherewith.

The eifectiveness of the seal in preventing entry of well fluid I2 intothe motor casing 2|] alon the motor shaft I8, for a given rotationalspeed, is dependent upon a minimum excess pressure of the internal motorfluid as compared with the pressure of the well fluid I2 at the seal. Byproviding such an excess pressure, any leakage, however small, that mayoccur is of motor fluid outwardly of the casing 20. Accordingly, thepurity of the internal motor fluid is maintained, insuring againstcontamination of the operating parts of the motor I4.

A reservoir for the internal motor fluid is conveniently provided as apart of the submersible structure. For this purpose, the lower endbracket 22 may be of inverted cup-shaped configuration, providing amotor fluid chamber 29 immediately beneath the bearing 24. A plate 30extends across the end of the bracket 22. Depending from the plate 30 isa boss 3I having a through aperture 32 leading to chamber 29. A flexiblemetal bellows 33 has a mouth 33a circumscribing the boss 3| and issecured thereto. Accordingly, the interior of the flexible bellows 33 isin communication with the chamber 29 and the interior of the motorcasing by way of the aperture 32.

Any pressure exerted on the exterior of the bellows 33 will necessarilybe communicated to the internal motor fluid, the bellows 33 forming apart of the internal motor fluid reservoir. It is not suflicient,merely, that the exterior of the bellows 33 be subjected directly to thewell fluid; substantially more pressur is necessary in order to achievethe desired operation of the seal while the unit is in operation.

To supply such pressure to the external portion of the bellows 33 and,thereby, to the motor fluid, there is illustrated in Fig. 1 a pressurechamber 34 formed by a supplementary rigid housing 35 carried by bracket22, This housing 35 substantially circumscribes the bellows 33, but isout of fluid-conducting relation with the interor of the bellows 33.

The chamber 34 is filled with well fluid I2. A conduit 36 communicatesthe pressure developed within the pump I3 to the chamber 34.Accordingly, when the unit is operating, the pressure of the pump, or aportion thereof, is communicated to the fluid within the pressurechamber 34. The pressure of the fluid in chamber 34 is transmitted tothe internal motor fluid through the flexible bellows 33 forming a partof the reservoir therefor.

The effectiveness of the seal is dependent upon the rotational speed ofthe device. By utilizing the pressure developed by the pump I3 to supplysuch excess pressure, the requirements for the effective operation ofthe seal are satisfied, since the pressure communicated by the conduit36 is the pressure developed by the pump, in turn dependent upon thespeed of rotation of the apparatus.

In Fig. 2 there is illustrated a modified form of this invention, whichaccomplishes the result of supplying an excess pressure to the internalmotor fluid. In this instance, a pressure chamber 40 is provided by asupplementary rigid hous- 4 ing 4! attached to the bracket 22. Thechamber 40 is in this instance sealed.

In the pressure chamber 40 there is provided a small quantity ofvolatile fluid 42. pressure due to the fluid 42 is communicated to theinternal motor fluid through the flexible bellows 33, therebymaintainingsuchexcess of pressure as is necessary for successfuloperation of the seal.

Ordinarily, the conditions under which the submersible structure can,between limits, be anticipated. Accordingly, the fluid may be chosenwhich best fulfills the requisites of the system, giving due regard tothe temperature, the depth at which the system operates, and the desiredminimum pressure differential required for the particular type of seal.Fluids such as methyl chloride, butane, and propane may be used.

The amount of fluid 42 used, while small, is such that for all limits ofoperation, sufiicient fluid 42 is available to supply the necessarypressure. i r I The inventor claims:

1. In a submersible structure adapted to operate in a well or the like:a motor having a casing and a shaft extending beyond said casing; a pumpoperated by said motor and coupled to said shaft; rotary and non-rotaryelements carried by the shaft and the casing respectively. said elementsbeing in engagement with each other to form a seal between said motorcasing and said shaft to exclude well fluid from said casing; meansforming a reservoir in communication with the interior of said casing,including a flexible bellows; means forming a pressure chambercontiguous with said bellows, but out of fluid conducting relation withthe interior thereof; a liquid completely filling the casing and thereservoir; and conduit means connecting said pressure chamber and theoutlet side of said pump for elevating the pressure of said internalliquid to create a presure drop across said seal from the interior ofthe casing.

2. In a submersible structure adapted to operate in a Well or the like:a motor having a casing and a shaft extending beyond said casing; rotaryand non-rotary elements carried by the shaft and the casingrespectively, said elements being in engagement with each other to forma seal between said motor casing and said shaft to exclude well fluidfrom said casing; said casing being adapted to contain internal'fluid;means forming a reservoir for said internal fluid, and in communicationwith the interior of said casing, including a flexible bellows; meansforming a sealed pressure chamber contiguous with said bellows, but outof fluid conducting relation with the interior thereof; and a volatilefluid in said pressure chamber for exerting a pressure on said bellowsto elevate the presure of said internal fluid to create a pressure dropacross said seal from the interior of the casing; the amount of volatilefluid being such with respect to the size of the pressure chamber as toprovide both a vapor and a liquid phase in said pressure chamber.

3. In a submersible structure: a motor having a shaft; a substantiallycylindrical casing sur-, rounding said motor; a first bracket for oneend of said casing, said shaft extending through said bracket; meanscarried by said first bracket forming a seal between said shaft and theexterior of said first bracket; a second bracket for the other end ofsaid casing, said second bracket being of cup shaped configurationfacing longi- The vapor tudinally outwardly of said casing, said secondbracket being adapted to carry a bearing structure for the end of theshaft, said second bracket forming a space beyond said shaft and alignedtherewith, said space being in communication with the interior of saidcasing; a plate accommodated on the open portion of said second bracket,said plate having an apertured boss extending outwardly of said spaceand aligned with said shaft; a flexible bellows accommodated on saidboss, the interior of said bellows being in communication with saidspace; said bellows, said casing, and said space being adapted tocontain an inert fluid; a housing surrounding said bellows and securedto said second bracket, said housing forming a pressure chamber for saidbellows; and means for supplying pressure to said pressure chamber forelevating the pressure of said fluid.

4. In a submersible structure: a motor havin a shaft; a substantiallycylindrical casing surrounding said motor; a first bracket for one endof said casing, said shaft extending through said bracket; a pumpoperated by said motor and coupled to said shaft; means carried by saidfirst bracket forming a seal between said shaft and the exterior of saidfirst bracket; a second bracket for the other end of said casing, saidsecond bracket being of cu shaped configuration facing longitudinallyoutwardly of said casing, said second bracket being adapted to carry abearing structure for the endof the shaft, said second bracket forming aspace beyond said shaft and aligned therewith, said space being incommunication with the interior of said casing; a plate accommodated onthe open portion of said second bracket, said plate having an aperturedboss extending outwardly of said space and aligned with said shaft; aflexible bellows accommodated on said boss, the interior of said bellowsbeing in communication with said space; said bellows, said casing, andsaid space being adapted to contain an inert fluid; a housingsurrounding said bellows and secured to said second bracket, saidhousing forming a pressure chamber for said bellows; and conduit meansconnecting said pressure chamber and the outlet side of said pump forelevating the pressure of said fluid.

5. In a submersible structure adapted to opterior of said casing,including a flexible bellows; means forming a sealed pressure chambercontiguous with the bellows, but out of fluid conducting relation withthe interior thereof; a liquid completely filling the casing and thereservoir; and a volatile fluid in said pressure chamber for exerting apressure on said bellows to elevate the pressure of the liquid in saidcasing and said reservoir to create a pressure drop across said sealfrom the interior of the casing; the amount of volatile fluid being suchwith respect to the size of the presure chamber as to provide both avapor and a liquid phase in said pressure chamber.

6. In a submersible structure: a motor having a shaft; a substantiallycylindrical casing surrounding said motor; a first bracket for one endof said casing, said shaft extending through said bracket; means carriedby said first bracket forming a seal between said shaft and the exteriorof said first bracket; a second bracket for the other end of saidcasing, said second bracket being of cup shaped configuration facinlongitudinally outward of said casing, said second bracket bein adaptedto carry a bearing structure for the end of the shaft, said secondbracket forming a space beyond said shaft and aligned therewith, saidspace being in communication with the interior of said casing; a plateaccommodated on the open portion of said second bracket, said platehaving an apertured boss extending outwardly of said space and alignedwith said shaft; a flexible bellows acocmmodated on said boss, theinterior of said bellows being in communication with said space; saidbellows, said casing, and said space being adapted to contain an inertfluid; a housing surrounding said bellows and secured to said secondbracket, said housing forming a sealed pressure chamber for saidbellows; and a volatile fluid in said pressure chamber for exerting apressure on said bellows to elevate the pressure of said inert fluid tocreate a pressure drop across said seal from the interior of the casing;the amount of volatile fluid being such with respect to the size of thepressure chamber as to provide both a vapor and a liquid phase in saidpressure chamber.

References Cited in the file of this patent UNITED STATES PATENTS

